Breathe a sigh of relief at NASA: One of the most delicate phases in the commissioning of the new James Webb Space Telescope worked – the unfolding of the sun shield. 107 retaining bolts had to loosen smoothly and in the correct sequence in order to unfold the protective shield the size of a tennis court. This step was successfully completed on the New Year, as NASA announced. Now the five wafer-thin membranes of the sun protection are slowly pulled smooth and stretched.
The James Web Web Telescope is the largest, most complicated and most expensive instrument that humanity has ever sent into space. On December 25, 2021, an Ariane 5 rocket brought the valuable telescope on its way to Lagrangian point L2. But before the high-resolution infrared telescope can begin its work, it has to be a complicated one Unfolding process go through, which gives NASA officials 29 days of anxiety.
107 retaining bolts and two telescopic struts
The James Webb Telescope has now successfully completed the first and most important part of this development: After the observatory had ignited the engines and set course for its target, the five-layer sunshield and its retaining struts were then folded out and extended. To do this, the ensemble’s tarpaulin rolled back first, then on New Year’s Eve the NASA deployment team began to extend the two central struts of the shield.
“These central struts do the main work and pull the membranes into their iconic diamond shape,” explains Keith Parrish of NASA. In order for this to happen, however, 107 retaining bolts had to be loosened completely and in the correct sequence – if only one bolt was stuck, unfolding threatened to fail.
But everything went well: All 107 bolts and actuators worked as planned and the sunshade was extended to the side with the help of two motors. On New Year’s Day, the protective shield then reached its full width of a good 14 meters.
Pause for measurements
“So far, the major development steps that we have taken have gone as smoothly as you could wish for,” says Mike Menzel, chief engineer of the deployment team. The chances are good that the James Webb telescope will get the cooling shade that its sensitive instruments need. Because only when the sun shield is fully functional and the optical side of the telescope shields from the heat radiation of the sun and earth, the mirrors can also be folded out.
“But before we go any further, let’s take the time to learn everything about how the telescope behaves under space conditions,” explains Menzel. Because all steps of the complex process and each component were tested in cold chambers and under vacuum conditions before the start. “We only had a week to find out how the telescope behaves in space,” says the NASA engineer.
Next step: tensioning the sunshade
The next step is another delicate phase: the tension in the five layers of the sun shield. The 0.025 to 0.05 millimeter thin membranes are slowly tensioned one after the other using a system of 90 pull ropes until they no longer touch each other. The resulting gaps are important so that the heat can escape. The tensioning process begins with the outer and largest membrane of the sunshade and is then continued successively for the other layers.
In this process, it is crucial that the motors work together with millimeter precision. The deployment team must therefore ensure that the engines are also at the optimal working temperature – not an easy task under the conditions of space. It will take at least two days to fully open the membranes, and possibly longer – depending on how often the NASA team interrupts the process.
At the interactive stage you can see at which stage the James Webb Telescope is and which steps have already been completed Deployment Explorer follow NASA.
What: NASA